The present invention is generally related to data communications and, more particularly, is related to a system and method for interfacing between a single media access controller to a number of physical layer devices.
In the field of data communications, there are many types of networks that facilitate the transfer of data from one location to another. Some exemplary standards include Ethernet, X.25, Frame Relay, and Asynchronous Transfer Mode. Generally these standards are available from standards bodies such as the Institute of Electrical and Electronics Engineers (IEEE) and other organizations. The standards generally describe how the data is to be packaged and then transported across the particular network and also provide for error checking and other aspects of data transmission as they relate to the particular standard in question.
With particular focus to Ethernet networks, the standards that guide the creation and operation thereof include the IEEE Std 802.3-1995, the entire text of which is incorporated herein by reference. The IEEE Std 802.3-1995 generally discusses Ethernet networks as they relate to the Data Link and Physical layers of the International Organization for Standardization Open Systems Interconnection (ISO/OSI) Reference Model which is well known by those skilled in the art.
In the Physical and Data Link layers, the IEEE Std 802.3-1995 particularly discusses the specifications and operation of the Media Access Controller (MAC) of the Data Link layer and the physical layer devices (PHYs) of the Physical layer. Also, the particular interconnection between the media access controllers and the physical layer devices is discussed, referred to as a Media Independent Interface (MII). As discussed in IEEE Std 802.3-1995, the MII may assume one of three following forms, including an integrated circuit to integrated circuit interface with traces on a printed circuit board, a motherboard to daughterboard interface between two or more circuit boards, or an interface between two printed circuit assemblies that are attached with a length of cable and an appropriate connector.
The data transfer accomplished with the MII as specified by IEEE Std 802.3-1995 provides for bi-directional data transfer. In each direction, the MII specifies a four bit bundle of conductors to transfer four bits of data or a single nibble in a four bit parallel data transfer. Also, the MII includes a transmit enable (TX_EN) conductor in each direction that provides a pathway for a TX_EN signal indicating that the nibbles are being presented on the MII for transmission. The IEEE Std 802.3-1995 also specifies that a single MII is to be employed between a media access controller and a respective physical layer device with which the media access controller communicates. Unfortunately, this requires a number of input and output pins to accommodate the MII interface between each media access controller and its associated physical layer device given that a single chip includes a number of media access controllers. This results in a significant number of pins that places a limit on the number of media access controllers within a specific integrated circuit due to size limitations as well as resulting in real estate problems on the integrated circuit itself.
In light of the foregoing, the present invention provides for a system and method in a media access controller for communicating to a number of physical layer devices. In one embodiment, the system comprises a common bus port for electrical coupling to a common bus that is electrically coupled to the physical layer devices, the common bus port including a parallel data port and an enable port. The system also includes a logical circuit to selectively transmit a data block to a respective one of the physical layer devices via the parallel data port. The logical circuit specifically precedes the transmission of the data block with the transmission of an address block that indicates the particular physical layer device to which the data block is to be transmitted.
In another embodiment, the present invention provides for a method for communicating to a number of physical layer devices via a media access controller. Broadly stated, the present method comprises the steps of: providing a common bus port in the media access controller for electrical coupling to a common bus that is electrically coupled to the number of physical layer devices, the common bus port including a parallel data port and an enable port, and transmitting a data block to a respective one of the physical layer devices via the parallel data port.
In still another embodiment, the present invention provides for a system and method in a physical layer device to receive data from the media access controller. In this regard, the system comprises a common bus port for electrical coupling to a common bus that is electrically coupled to a number of physical layer devices, the common bus port comprising a parallel data port and an enable port. The system also includes a logical circuit to maintain an address designation associated with the physical layer device and a logical circuit to receive an address block via the parallel data port. Finally, the system in the physical layer device comprises a logical circuit to receive a data block associated with the address block via the parallel data port. The physical layer device employs these elements to receive a data block that is associated with the received address block when the address block is equal to the address designation of the particular physical layer device.
The present invention can also be viewed as providing a method for receiving data in a physical layer device from a media access controller. This method can be broadly summarized by the following steps: providing for a common bus port in the physical layer device, the common bus port being adapted for electrical coupling to a common bus that is electrically coupled to a number of physical layer devices, the common bus port comprising a parallel data port and an enable port; maintaining an address designation associated with the physical layer device; receiving an address block from the media access controller via the parallel data port; and, receiving a data block associated with the address block from the media access controller via the parallel data port.